Electroplating apparatus for use with a phonograph record matrix



DeC- 3, 1968 R. Pcmmm'A ET AL 3,414,502

ELECTROPLATING APPARATUS FOR USE WITH A PHONOGRAPH R RD MATRIX FiledJan.

meir ArrbR/VEYS United States Patent O York Filed Jan. 18, 1965, Ser.No. 426,303 7 Claims. (Cl. 204-281) ABSTRACT OF THE DISCLOSURE Anelectroplating fixture which masks the rim of an object to beelectroplated in an electroplating bath from the bath and which includesa loop of elastomeric material formed with two opposed inner side faceswhich define a longitudinal recess in the loop adapted to receive therim of the object.

This invention relates to an electroplating fixture and, moreparticularly, to an improved apparatus for suspending an object by itsrim in an electroplating bath so that no metal is deposited on the rimand one side of theobject.

In the production of disc phonograph records, for example, severalelectroplating operations are performed in the manufacture of thenegative matrices or stampers from which the phonograph records areformed by a molding or pressing operation. A negative metal master isfirst formed from the original master into which the sound groove hasbeen cut. Then a positive mother plate is formed from the negative metalmaster. Finally, the stamper is formed from the mother plate. Thesethree operations are all carried out lby electroplating.

The thin metal matrix (original master, negative metal master or motherplate) is conventionally clamped to a more sturdy backup disc at thecenter through the usual center hole in the matrix. The backup disc hasone conductive face for making electrical contact with the matrix. Amasking ring is used to hold the periphery of the matrix to the backupdisc, but the conventional ring has several basic disadvantages. Itpermits metal to be plated around the outside edge or rim of the matrixresulting in an undesirable metal overlap. In order to permit theseparation of the matrix and the derivative part, it is necessary togrind, file, Vsand or cut the overlap. A high rejection rate of thederivative matrices results from these techniques, accompanied by acorresponding increase in cost for producing matrices and thereforephonograph records. Furthermore, the conventional masking rings do notprovide sufiicient clamping between the matrix and the backup disc, sothat an additional clamp at the center is required.

Accordingly, it is an object of the present invention to overcome theabove-mentioned difficulties of conventional electroplating fixtures forthin metal matrices such as those required in the production ofphonograph records.

Another object of the invention is to provide a novel electroformingmasking ring which prevents any metal overlap from being electroplatedaround the rim of the matrix.

A further object of the invention is to provide an improved ring whichclamps the rim of a matrix so securely to a backup disc that noadditional clamping is required at the center of the matrix.

These and other objects and advantages of the invention are attained byproviding a ring formed with an annular recess adapted to receive thebackup disc and lthe matrix. The ring is preferably of elastomericmaterial, and in one embodiment the recess is formed between two3,414,502 Patented Dec. 3, 1968 rice side walls, at least one of whichhas an inner face sloping inwardly toward the other side wall. Inanother embodiment at least one of the side walls has a first inner facewhich slopes inwardly toward the other side wall and a second inner facewhich slopes from the first face inwardly away from the other side Wall.According to a third embodiment the two side walls have opposed innerfaces which are substantially parallel.

All of the above is more fully explained in the following detaileddescription of several preferred embodiments of the invention, thisdescription being illustrated by the accompanying drawings wherein:

FIG. 1 is a simplified perspective view, partially in schematic form, ofan electroplating -bath including a fixture embodying the presentinvention, wherein a matrix is clamped to a backup disc by a maskingring;

FIG. 2 is an enlarged sectional view of the fixture taken along the line2--2 of FIG. l;

FIG. 3 is an enlarged fragmentary view in section of the fixture of FIG.2;

FIG. 4 is a fragmentary view in section of the masking ring of FIG. 3,the backup disc and the matrix Vbeing removed;

FIG. 4A is a fragmentary view in section of the matrix and thederivative part plated thereon after completing an electroplatingoperation employing the apparatus of FIGS. 1-4;

FIG. 5 is a fragmentary view in section illustrating another maskingring according to the invention clamping a matrix to a backup disc;

FIG. 6 is a fragmentary View in section of the masking ring of FIG. 5,the backup disc and the matrix being removed;

FIG. 6A is a fragmentary view in section of the matrix and thederivative plate after completing an electroplating operation employingthe masking ring of FIGS. 5 and 6; and

FIG. 7 is a fragmentary view in section showing still another maskingring according to the invention.

In the typical embodiment of the invention shown in FIGS. 1-4, a tank 10contains a suitable electrolyte 11. Suspended in the electrolyte are acathode 12 and an anode 13, the anode being of the material to bedeposited on the cathode. The electrodes 12 and 13 are electricallyconnected to a source 15 of direct current. The operation and techniquesof electroplating are well known and need not be explained here.

The cathode 12 includes the matrix 16, the side 17 0f which carries theprogram information which is eventually to be pressed or molded into thefinished phonograph record. In producing the negative matrix or stamperfrom which the record is formed, several derivative matrices aresuccessively formed by electroplating. In each operation the new part isplated onto the side 17 of the original part or matrix 16.

The matrix 1-6 is clamped to a backup disc 18 which is preferably ofelectrically non-conductive material but has an electrically conductiveface (not shown) adapted to make contact with the matrix. The backupdisc is mounted at its center to a shaft 19 of an electricallyconductive material such as copper which makes electrical contact at oneend with the electrically conductive face, the opposite end of the shaftbeing adapted to be connected to the source 15. The shaft is encased ina suitable insulating cover 20, except for its free end, so that nometal is deposited on the shaft during the electroplating operation.

The rim of the matrix is clamped to the rim of the backup disc by amasking ring 21, which is preferably made of an elastomeric materialsuch as rubber. The masking ring, when viewed in cross-section, includesa backup wall or first side wall 22 extending radially inwardly, .e.,towards the center of the ring, which s adapted to abut the backup disc18, and an end wall 23 extending substantially perpendicularly from thebackup wall. The end wall is formed with a second side wall or flange 24extending radially inwardly therefrom, so that an annular recess 25 isformed between the backup wall and the ange. The inner face 26 of theflange slopes from the end wall inwardly toward the backup wall to a rim27. The distance from the rim to the backup wall is preferably less thanthe combined width of the backup disc 18 and the matrix 16, while thewidth of the recess at the end wall is greater than this combined width.When the masking ring is snapped over the rims of the backup disc andthe matrix, the end wall and the flange are flexed slightly outwardly(see FIG. 3), and the matrix is securely clamped to the backup disc, thegreatest force being applied at the rim 27. Due to the excellentclamping action at the rim of the matrix, no additional clamping isrequired at the center of the matrix as is necessary with conventionalmasking rings, so that it is possible to produce matrices Without centerholes with a masking ring according to the present invention. It isapparent that this masking ring can also be used in the production ofmatrices with center holes, if desired.

Furthermore, there is no creep of metal deposit past the point ofcontact between the rim 27 and the matrix 16 to form a metal overlaparound the rim of the matrix. FIG. 4A illustrates in full lines the rimof the new part or derivative matrix 30 which is electroplated onto theside 17 of the matrix 16 when the matrix is clamped by the ring 21. Themetal overlap around the matrix 16 which is permitted by conventionalmasking rings is shown in phantom at 31. It is apparent that thisoverlap must be removed by grinding, filing, sandingr or cutting, whichis not only costly in itself but is destructive of a considerable numberof derivative matrices. In contrast, the new part 30 is readily strippedor separated from the matrix 16 by hand, no tools being required.

The derivative matrix produced by each electroplating Operation has adiameter slightly smaller than the original matrix (see FIGS. 4A and6A), but one masking ring can be used for the several electroplatingoperations in the manufacture of stampers, inasmuch as the ring is ofelastomeric material and is stretched around the matrix and the backupdisc.

It can be seen that a small bead 32 is formed at the rim of the new part30. This bead is caused at the region of high current density adjacentthe rim 27, because of the slope of the lower face 33 of the iiange 24outwardly from the rim. Although this bead does not impede the strippingof the original and derivative matrices, it can be eliminated, ifdesired, by using a masking ring 35 of the type illustrated in FIGS. 5and 6. Like parts in these figures and in FIGS. 3 and 4 respectively,are designated by like primed reference numerals in FIGS. 5 and 6. The

iiange 36 extending from the end Wall 23 is provided i with a Shieldinglip so that the flange has a first inner face 26 sloping from the endwall inwardly toward the backup Wall 22 to a rim 27, and a second innerface 37 sloping from the rim 27' inwardly away from the backup wall. Thedistance from the rim 27 to the backup wall and the width of the recessat the end wall are preferably less than and greater than, respectively,the combined width of the matrix and the backup disc. When the matrixand the backup disc are inserted into the recess 25 they are securelyclamped as before, but there is a region of low current density adjacentthe rim 27', inasmuch as the second inner face 37 slopes inwardly whilethe lower face 33 of the iirst embodiment slopes outwardly. FIG. 6Ashows the shape of the rim 38 of the new part 39 which is formed on thematrix 16 when the matrix is `clamped to the backup disc by the ring 35.This rim 38 is shaped in conformity with the second inner face 37 of thering 35 as viewed in FIG. 5.

FIG. 7 illustrates still another embodiment of the invention in which amasking ring 40 of generally circular cross-section is formed with twoside Walls 41 and 42 spaced by an end wall 43. The inner faces 44 and 45of the side walls 41 and 42, respectively, are substantially paralleland are so spaced that the backup disc and the matrix are snuglyreceived in the annular recess 46 formed thereby, that is, the two sidewalls are slightly spread by the backup disc and the matrix. If a beadat the rim of the derivative plate is to be avoided, the ends of theside walls 41 and 42 may be formed with shielding lips similar to theone illustrated in FIGS. 5 and 6.

Although this invention has been described with reference to specificembodiments, modifications and variations will readily occur to thoseskilled in the art. For example, an object other than a phonographrecord matrix may be clamped at its rim to the rim of an appropriatesupport member by any masking ring according to the present inventionfor suspension in an electroplating bath. Furthermore, the masking ringcan be modified to take the form of a loop for use with an object Whoserim is not circular. In addition, the masking ring may be used to maskthe rim of an object to be electroplated from the electroplating bath ifthe object is supported by means other than a backup disc, for exampleif the object has a suitable hole by which it may be clamped to asupport member. Therefore, the invention is not to be construed aslimited to the physical embodiments described, but all such variationsand modifications are included within the intended scope of theinvention as defined by the following claims.

We claim:

1. Apparatus for supporting a phonograph record matrix to a backup dischaving an electrically conductive face engageable with the matrixcomprising a ring of elastomeric material including a backup wallextending radially inwardly and an end wall extending generallyperpendicularly from the backup wall, the end wall being formed with aange extending radially inwardly therefrom, the -backup wall and theflange forming a recess in which the backup disc and the matrix areadapted to be received, the tiange having a iirst inner face slopinginwardly toward the backup wall to form a rim, the distance between therim and the backup wall being less than the combined width of the backupdisc and the matrix, whereby the backup disc and the matrix flex theange to provide a clamping action in which the greatest force is appliedat the tiange rim so that the surfaces of the matrix under the ring andthe backup disc are masked from the electro-plating bath and additionalclamping of the matrix to the backup disc is unnecessary.

2. Apparatus according to claim 1 wherein the ange has a second innerface sloping from the rim inwardly away from the backup wall.

3. Apparatus according to claim 1 wherein the width of the recess at theend wall is greater than the cornbined width of the backup disc and thematrix.

4. Apparatus for suspending matrix in an electroplating bath so thatonly one side of the matrix is electroplated comprising a backup disc ofelectrically non-conductive material having an electrically conductiveface adapted to make contact with the matrix,

insulated means for conducting electrical current to the electricallyconductive face, and

a ring of elastometric material including an end wall and two side wallswhich form an annular recess adapted to receive the backup disc and thematrix.

5. Apparatus according to claim 4 wherein the side walls have opposedinner faces which are substantially parallel.

6. Apparatus according to claim 4 wherein at least one of the side wallshas an inner face sloping inwardly toward the other side wall.

7. Apparatus according to claim 4 wherein at least one of the side wallshas a first inner face sloping from the 6 end wall inwardly toward theother side Wall and a second 2,890,160 `6/ 1959 Hunting et al. 204-2813,239,443 3/1966 Bryan et al. 204-196 inner face sloping inwardly awayfrom the other side wall.

FOREIGN PATENTS Referencs Cited UNITED STATES PATENTS 5 4941193 3/1930Germany- 1,226,856 5/1917 Bradley 118-500 2,731,947 1/1956 Harder 118500 HOWARD S. WLLIAMS,Prlma1y Exammer.

D. R. JORDAN, Assistant Examiner.

2,153,188 4/1939 Hickman.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No.3,414,502 December 3, 1968 Louis R. Porrata et al.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 4, line 32, after "matrix" insert in an electroplating bath andadapted to clamp the matrix line 56, after "suspending" insert Signedand sealed this 17th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. F letchei', Jr.

Commissioner of Patents Attesting Ufficer

